Single or three-phase load-breaking switch with permanent magnet actuator assembly



Se t. 13, 1966 .1. c. CLASON 3, SINGLE OR THREE-PHASE LOAD-BREAKING SWITCH WITH PERMANENT MAGNET ACTUATOR ASSEMBLY Filed March 3, 1964 INVENTOR N (fl/1:0)!

U 4 A2101. BY M ATTORNEY;

United States Patent 3,272,939 SINGLE 0R THREE-PHASE LOAD-BREAKING SWITCH WITH PERMANENT MAGNET AC- TUATOR ASSEMBLY Jan Christiaan Clason, Hengelo, Netherlands, assignor to N.V. Fabriek van Electrische Apparaten Voorheen F. Hazemeijer 8; Co., Hengelo, Netherlands, a corporation of the Netherlands Filed Mar. 3, 1964, Ser. No. 349,094 Claims priority, application Germany, Mar. 4, 1963, N 22,844 2 Claims. (Cl. 20082) A three-phase load-breaking isolating switch for separate switching in and out of the loads on the individual phases is known, having in each phase a fixed contact pair and a movable bridging contact for each fixed contact pair. This bridging contact is movable within a switching hood and is subjected within such hood to spring pressure exerted in inward direction. In the closed condition of the switch the bridging contact is held in place and yieldingly pressed against the fixed contacts through its own armature plate by permanent magnets on the fixed portion of the switch. This known switch has the property, that the controlled circuit can be very quickly opened and the switch therefore makes possible an instantaneous tripping of the load circuit. When for opening the load circuit the switching hood is withdrawn from the fixed portion of the switch, the above-mentioned springs in the hood are stressed and the armature plate then frees itself from the fixed permanent magnets, whereupon the movable bridging contact is very quickly withdrawn from the fixed contacts.

The invention effects improvements in the above-mentioned known switch such that it not only permits remote control, but also becomes a switch having so-called rapid closure. The invention is applicable both to single-phase and to three-phase switches of the above-mentioned kind.

The invention is characterized in that the piston rod of a pneumatic piston is rigidly connected to the movable switching hood of a single-phase load-breaking isolating switch of the above-mentioned kind or to the movable switching hoods of all phases of a three-phase loadbreaking isolating switch of the above-mentioned kind, and in that a plate of magnetically soft material is mounted on the piston rod and is held in place in the open condition of the switch by a fixed permanent magnet system associated with the piston.

One construction according to the invention will now be described with reference to the drawing as applied to a three-phase load-breaking isolating switch of the abovementioned kind. The fixed portion of the switch, which carries the fixed contacts, is not shown in the drawing.

The drawing shows a framework, into which the known load-breaking isolating switch is built. This framework is illustrated as consisting of a horizontal girder 10 at the top of the framework and two vertical girders 11 and 12. The movable switching hoods 13, 14, 15 of the switch are all secured on a common transverse beam 16 in a manner not of detailed interest here, that is, are connected as a unit to such beam 16. Above a circular opening 17 in the middle of the girder 10 is a cylinder, which consists of a foot 18 and a tube 19 and in Which a piston 20 can slide. Within the foot 18 of the cylinder in a housing 21 is mounted an annular magnet system consisting of an outer pole ring 22, an inner pole ring 23 and an annular permanent magnet 24 between these two pole rings. The direction of magnetisation of the annular permanent magnet 24 is radial, so that, say, the inner pole ring 23 is the south pole and the outer pole ring 22 the north pole of the permanent magnet. Within the inner pole ring 23 of the annular magnet system passes a piston rod 25, which is rigidly connected at its upper end to the piston 20 and at its lower end to the beam 16. The elements 26 and 27 shown in the drawing between the piston rod 25 and the piston 20 can for the moment be disregarded. Loosely mounted on the piston rod 25 at its lower end is a circular plate 28 of magnetically soft material, which in the position of the piston 20 shown lies against the lower end faces of the pole rings 22 and 23 and is held there by the annular permanent magnet 24. At 29 are shown two spring discs 29, which are inserted between the circular plate 28 and the common beam 16 carrying all the switching hoods of the switch.

When the switch shown in the drawing is to be closed, compressed air is introduced into the space above the piston 20, so that the pressure in this space increases. The piston 20, however, remains at rest, until the force exerted on the upper face of the piston overcomes the attraction of the annular permanent magnet 24 on the circular plate 28, whereupon the switching hoods 13, 14, 15 of the switch, which are connected together on the beam 16, begin to move very quickly downwards, and the loadbreaking isolating switch is thus quickly closed.

The load-breaking isolating switch is thus not only very quickly closed, but also by means of the arrangement illustrated can be actuated from a remote point through a compressed air control conduit.

In the losed condition of the switch, the piston 20 has been moved downwards from the position shown in the drawing to a position in which an annular plate 26 similar to the circular plate 28 engages with the upper end face of the pole rings 22 and 23. In order to prevent damage to this plate 26, when it strikes the upper end face of the pole rings 22 and 23, spring discs 27 are provided above the annular plate 26.

The opening movement of a switch of the kind shown in the drawing, including the annular plate 26 and the spring discs 27 takes place in the following manner. The pressure beneath the piston 20 is gradually increased through a compressed air conduit until the force acting on the underside of the piston overcomes the magnetic force exerted on the annular plate 26. The beam 16 then moves quickly upwards, so that all phases of the isolating switch are quickly opened.

It should be mentioned that in the known three-phase load-breaking isolating switch, the unavoidable ditferences in the armature plates and permanent magnets in the individual phases cause undesirable time dilferences to occur in the interruption of the three individual phase circuits on hand opening of the three-phase switch. Since these time differences can lead, especially with relatively high loads, in certain circumstances to considerable disturbances, the switch according to the invention, if provided with the annular plate 26, represents a marked technical advance, since with the quick opening of the isolating switch described the time intervals between the moments of interruption of the individual phase circuits are so small as to be wholly negligible.

What I claim is:

1. An actuator assembly system for a load-breaking isolator switch comprising a movable hood assembly adapted to contain switch contacts which may be opened and closed by movement of the hood between two limiting positions, a housing for conveying controllable pneumatic pressure, a piston reversibly movable within said housing responsive to said pressure, a piston rod rigidly connected to both the movable hood assembly and the piston to move the hood between said limiting positions responsive to the pneumatic pressure, a permanent magnet system afiixed within said housing to intercept respectively the path of said piston and said hood near corresponding ones of the two limiting positions, and two plates of magnetically soft material aflixed to said piston rod respectively near the hood and piston to move therewith and intercept said permanent magnet system to magnetically engage the permanent magnet system at the respective limits and hold said piston rod in place wherefrom the contacts may be changed by breaking the plates away from the magnet quickly only after said pneumatic pressure is changed on said piston to an extent exceeding the holding force of the magnet on said plates.

2. An actuator assembly system as defined in claim 1 for a three phase circuit wherein the hood assembly comprises three separate hoods each adapted to contain a single phase load-breaking isolating switch, and a member connecting all three hoods to said piston rod for movement of the corresponding switches simultaneously between said tWo limiting positions.

References Cited by the Examiner UNITED STATES PATENTS 2,509,008 5/1950 McFarland 200-87 X r 2,847,528 8/1958 Combs 20087 X 2,922,002 1/1960 Gilman 2'0083 3,042,771 7/ 1962 Oliveau 200-67 X 3,109,908 11/1963 Cl-ason 20087 X BERNARD A. GILHEANY, Primary Examiner.

H. M. FLECK, Assistant Examiner. 

1. AN ACTUATOR ASSEMBLY SYSTEM FOR A LOAD-BREAKING ISOLATOR SWITCH COMPRISING A MOVABLE HOOD ASSEMBLY ADAPTED TO CONTAIN SWITCH CONTACTS WHICH MAY BE OPENED AND CLOSED BY MOVEMENT OF THE HOOD BETWEEN TWO LIMITING POSITIONS, A HOUSING FOR CONVERYING CONTROLLABLE PNEUMATIC PRESSURE, A PISTON REVERSIBLY MOVABLE WITHIN SAID HOUSING RESPONSIVE TO SAID PRESSURE, A PISTON ROD RIGIDLY CONNECTED TO BOTH THE MOVABLE HOOD ASSEMBLY AND THE PISTON TO MOVE THE HOOD BETWEEN SID LIMITING POSITIONS RESPONSIVE TO THE PNEUMATIC PRESSURE, A PERMANENT MAGNET SYSTEM AFFIXED WITHIN SAID HOUSING TO INTERCEPT RESPECTIVELY THE PATH OF SAID PISTON AND SAID HOOD NEAR CORRESPONDING ONES OF THE TWO LIMITING POSITIONS, AND TWO PLATES OF MAGNETICALLY SOFT MATERIAL AFFIXED TO SAID PISTON ROD RESPECTIVELY NEAR THE HOOD AND PISTON TO MOVE THEREWITH AND INTERCEPT SAID PERMANENT MAGNET SYSTEM TO MAGNETICALLY ENGAGE THE PERMANENT MAGNET SYSTEM AT THE RESPECTIVE LIMITS AND HOLD SAID PISTON ROD IN PLACE WHEREFROM THE CONTACTS MAY BE CHANGED BY BREAKING THE PLATES AWAY FROM THE MAGNET QUICKLY ONLY AFTER SAID PNEUMATIC PRESSURE IS CHARGED ON SAID PISTON TO AN EXTENT EXCEEDING THE HOLDING FORCE OF THE MAGNET ON SAID PLATES. 